Alexander Duscheleit posted on Sat, 02 Jan 2016 11:53:18 +0100 as excerpted:
> I was under the impression that a mount (actually any) command issued > against a member of a multi-device btrfs would affect the whole > multi-device. Well, yes and no. Yes, when it mounts correctly. But with a multi-device btrfs, it can happen that btrfs doesn't yet know about all the devices when a mount is attempted, in which case the mount may fail (particularly without the degraded option), simply because it doesn't know about the other devices. A btrfs device scan after all devices are available but before the mount attempt should fix this problem and allow a mount with any of the component devices, and these days, udev normally triggers that when any new devices appear, so it seldom needs to be done manually. However, in udev-free cases or in early boot before udev is up, udev obviously won't handle it and the mount can still fail. Additionally, if a device is missing or damaged to the point that btrfs can't see it, btrfs will normally refuse a mount unless degraded is one of the mount options. And depending on the situation, degraded,ro may be needed. While you mentioned below this part in your reply that you had tried degraded,ro, that wasn't in your original post, so we wanted the mount options you had actually tried, to see if you had tried degraded,ro, or not. -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
